The present invention pertains to a combustion air blower, especially an annular channel blower, for an auxiliary heater for a motor vehicle. The invention relates more particularly to a combustion air blower in which the suction side of the blower is connected to the delivery side via a bypass channel, which has an adjustable throttling member, in a communicating manner.
In combustion air blowers of this kind, the bypass channel with the throttling member located therein has the task of setting the air throughput of the blower within certain limits without causing any appreciable change in the power consumption of the blower motor.
In a prior-art combustion air blower (West German Patent Specification No. 32,09,904), the throttling member is designed as an adjusting screw. However, this requires the preparation of a female thread running perpendicularly to the longitudinal axis of the bypass channel. Because the housing of the combustion air blower usually consists of a plurality of injection molded parts, and particularly the part containing the bypass channel is an injection molded part, a separate operation is required to prepare the female thread for the adjusting screw after the molding of the part.